1. Field of the Invention
The present invention relates to an agent for disintegrating gallstones, and more particularly to an agent for disintegrating gallstones containing an alkali metal carbonate or a combination of an alkali metal carbonate and N-acetylcysteine as its effective components.
2. Related Arts
The statistical study shows that gallstone carriers reach about 9% of the population in Japan. In 1989, the cholecystolithiasis patients were reported to be 270,000, most of whom were subjected to surgical lithectomy. The gallstones are classified into cholesterol gallstones and pigment gallstones (bilirubin calcium and black-pigment stones) based on the component thereof. Studies on an agent for dissolving gallstones have been performed for a long time, resulting in the development of formulations of bile acid such as ursodeoxycholic acid and chenodeoxycholic acid for dissolving choresterol gallstones. Clinical tests have proved that such formulations are effective for gallstone dissolution. However, actual effect for gallstone dissolution given by such formulations depends on the size of the stone and cholecyst function, whereby the patient should be dosed for a long period such as a half- year to a year or more. A suitable agent for dissolving pigment stones has not yet been developed in spite of various studies.
The inventor has found out from studies on composition of the gallstones that mucopolysaccharides and mucoproteins (hereinafter abbreviated to muco-substances) play an important role as a component for binding the crystalline cholesterol or bilirubin. On the other hand, SH-compounds including N-acetylcysteine have been known to have action for splitting off the S--S bond of muco-substances. In particular, it has been reported that N-acetylcysteine accelerates dissolution of cholesterol gallstones [see Scand. J. Gastroent., 24, 373-380 (1989); Gastroenterology., 98, 454-463 (1990)]. However, this document reports that the dissolution of cholesterol gallstones takes about 10 hours to several weeks, and further that the absolute effect is small.
On the other hand, the effective action of alkali metal carbonates for disintegrating gallstones has not been known.
Under such circumstance, it is desired to develop an agent which can easily destroy gallstones to make their small pieces which can be removed without surgical lithectomy.